This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to Japanese Application No. 2000-225707 filed on Jul. 26, 2000, the entire content of which is incorporated herein by reference.
The present invention generally relates to an actuator for operating a door. More particularly, the present invention pertains to an actuator for effecting the opening, closing, locking and/or unlocking operation of a vehicle door.
Japanese Patent Laid-Open Publication No. 2000-27508 discloses a known actuator for operating a vehicle door. The known actuator for operating a door includes an electric motor, a deceleration gear mechanism, and an output member operatively connected to the electric motor via the deceleration gear mechanism. The output member is operated from an initial position to a predetermined operational position through actuation of the electric motor via the deceleration gear mechanism.
In this known vehicle door operating actuator, the deceleration gear mechanism includes a return spring. The deceleration gear operates the output member from an initial position to a predetermined operational position while deflecting the return spring upon actuation of the electric motor. After stopping operation of the electric motor, the output member returns from the operational position to the initial position by reverse operation of the deceleration gear through the biasing force of the return spring.
With the known actuator mentioned above, including the deceleration gear mechanism having the return spring for enabling returning operation of the output member, the return spring is deflected by the deceleration gear mechanism while operating the output member from the initial position to the operational position. Accordingly, the driving torque of the electric motor transmitted to the output member is partly lost by the deflection of the return spring. Further, because the return spring is gradually deflected in accordance with the operation of the output member, the driving torque loss of the electric motor is gradually increased and so it becomes difficult to operate the output member at a constant driving torque. Hence, considering the loss of the driving torque, a relatively large size electric motor is necessary for ensuring sufficient driving torque for the output member. As a result, the size of the actuator is increased.
A needs thus exists for an actuator for operating a vehicle door in which the size of the electric motor, and the size of the overall actuator, is minimized.
According to one aspect of the invention, an actuator for operating a vehicle door includes an electric motor, a deceleration gear mechanism, an output member operatively connected to the electric motor via the deceleration gear mechanism and operable from an initial position to a predetermined operational position, and a spring disposed between the deceleration gear mechanism and the output member to effect a frictional connection with the output member and the deceleration gear mechanism for connecting and disconnecting the deceleration gear mechanism and the output member. The output member and the deceleration gear mechanism are connected to one another by the frictional connection of the spring with the deceleration gear mechanism and the output member during actuation of the electric motor to move the output member to the operational position, and the output member is returned from the operational position to the initial position by release of the frictional connection to separate the deceleration gear mechanism and the output member when operation of the electric motor is stopped.
According to another aspect of the invention, an actuator for operating a vehicle door includes a housing, an electric motor accommodated in the housing and having an output shaft, a worm gear engaged with the output shaft of the electric motor, a wheel gear rotatably supported in the housing and engaged with the worm gear, and a first output member rotatably supported in the housing coaxially with the wheel gear. The first output member and the wheel gear each have a shaft portion. A spring case is supported by the housing and a spring is accommodated in the spring case. The spring is disposed around the shaft portion of the wheel gear and the shaft portion of the first output member for frictionally engaging an outer peripheral surface of the shaft portion of the wheel gear and an outer peripheral surface of the shaft portion of the first output member. One end of the spring is maintained by the wheel gear and the other end of the spring is maintained by the spring case.
In accordance with a further aspect of the invention, an actuator for operating a vehicle door includes a housing, an electric motor mounted at the housing, a wheel gear rotatably mounted at the housing and operatively connected to the motor to rotate in response to operation of the motor, an output gear rotatably mounted at the housing, a rotatable output member operatively connected to the output gear to rotate in response to rotation of the output gear to move from an initial position to an operational position, and a spring disposed adjacent the wheel gear and the output gear to frictionally engage the wheel gear with the output gear upon operation of the motor to operationally connect the wheel gear and the output gear so that rotational movement of the wheel gear is transferred to the output gear and then to the output member to move the output member from the initial position to the operational position.